where do you buy differt kinds of colored marble dust, like red marble dust, white marble dust, black marble dust.
Run a google search. There's all kinds of sources.
you can mix marble dust with a urethaen resin wich is not as smelly as epoxy resin it also sets faster and can be bought from most resin suppliers on the web you can then use colour pigments and colour it any shade you like
you don't buy different colours you colour it your self.